Under the direction of their math teacher, Richard McKeon, these students
had a great time constructing the computer on a 4 x 8 foot sheet of
plywood. Not only was this a fun project, but an excellent learning
experience in computer architecture and logic. For details of construction
and wiring we used the book “How To Build A Working Digital
Computer” by Edward Alcosser.

The plywood sheet was sectioned off for the different
computer functions:

1.The drum memory was a piece of stove pipe with
several paper clip wipers. The program of instructions consisted of holes
cut in a sheet of graph paper that was wrapped around the drum. The drum
could be rotated so that one instruction at a time could be read.

2.Because digital computers use binary logic, we built an encoder
section to convert “regular” (base 10) numbers to binary. For this
we built our own rotary switches from thread spools wrapped with un-insulated
wire. The switches were programmed by wrapping tape around them that had
holes cut in appropriate places. The wipers again consisted of bent paper
clips.

3.To get the results of an operation back out of the computer
in base 10 numbers we built a decoder section using a series of
knife switches and lamps to display the decimal numbers.

4.For temporary storage while computing the core memory
consisted of paper clips bent in such a way that they could store a
“1” or a “0” by lighting (or not) a lamp.

5.To wire up the arithmetic unit we had to understand
how a series of knife switches could be arranged to perform binary
arithmetic and display the results.

Everyday we rescue items you
see on these pages!
What do you have hiding in a closet or garage?
What could you add to the museum displays or the library?